Wireless networks are increasingly commonly employed to provide enhanced capabilities for a variety of devices. One category of wireless networks is a wireless Personal Area Network (PAN). One suitable format for communications in a wireless PAN is described by the ZigBee Specification for low cost, low power wireless radio links, as defined by the ZigBee Alliance. ZigBee wireless PANs are especially suitable for use, for example, in home automation networks for controlling lights, security systems, fire alarms, heating-ventilation-and-air-conditioning (HVAC) systems, etc.
FIG. 1 shows one exemplary embodiment of a wireless network 100 including a plurality of wireless devices 120. Wireless network 100 may be a ZigBee wireless PAN. In the wireless network 100, wireless devices 120 are classified into three different categories: PAN Coordinator 120a, Routers 120b, and End Devices 120c. In the context of a ZigBee wireless PAN, each of these wireless devices 120 is also sometimes referred to as a “node.”
Each ZigBee wireless network includes a PAN Coordinator 120a. PAN Coordinator 120a is the ZigBee device responsible for starting the formation of the wireless network 100. PAN Coordinator 120a is able to store information about the wireless network 100 (e.g., security keys). PAN Coordinator 120a chooses for itself a PAN ID, and conventionally has a ZigBee address of 0.
Wireless network 100 may include a plurality of Routers 120b. Router 120b has the capability to pass data from one wireless device 120 to another wireless device 120, and may also act as a source and destination for data communications.
In contrast, End Device 120c includes just enough functionality to communicate with its “parent node”—which may be either a Router 120b or PAN Coordinator 120a. End Device 120c cannot directly pass messages between two other wireless devices 120. Accordingly, End Device 120c requires the least amount of memory and therefore in general can be manufactured at a lower cost than PAN Coordinator 120a or Router 120b. 
In a ZigBee wireless PAN, communication between nodes 120 takes place over one of a number of “physical channels.” ZigBee wireless PANs and wireless devices employ functionality described in IEEE Standard 802.15.4. IEEE 802.15.4 has two physical (PHY) layers that operate in respective upper and lower frequency ranges: 868/915 MHz and 2.4 GHz. The lower frequency PHY layer covers both the 868 MHz European band and the 915 MHz band, used in countries such as the United States and Australia. The higher frequency PHY layer is used virtually worldwide.
The 2.4 GHz communications band contains 16 separate IEEE 802.15.4 channels, so a number of ZigBee wireless PANs can operate simultaneously, with each operating on its own channel(s), thereby not interfering with each other. It is possible for more than one ZigBee wireless PAN to use a single channel, especially if they are separated by a long distance (>10-100 m away), or if both have fairly low usage rates (low duty cycle).
Other devices (e.g., so-called “WiFi” devices) also operate in the 2.4 GHz band, and WiFi traffic can interfere with ZigBee traffic. WiFi messages can be transmitted at a much higher power level than ZigBee messages, and a WiFi channel is as wide in bandwidth as several ZigBee channels. In order for two such systems to coexist it is beneficial to be able to work out which channels are clear, and to get the interfered-with network (e.g. the ZigBee wireless PAN) to operate on these clear channels.
Patent application WO IB2007/050704, which is incorporated herein by reference, describes a mechanism for reporting when an interference problem has been detected, such that some node 120, typically PAN Coordinator 120a, would be able to select a better channel on which to operate wireless network 100. It also discloses the possibility that PAN Coordinator 120a, on receiving an interference report from some other node 120 in wireless network 100, would request further nodes 120 to carry out an assessment of the local channel conditions, and report these back, further improving the likelihood of selecting a globally “good” channel.
Additionally, U.S. patent application 60/886,419 filed on 25 Jan. 2007 discloses improvements to the mechanism by which networked devices 120 assess locally how good or bad a channel is, and to how these are reported back to a central node 120 (e.g., PAN Coordinator 120a).
In that case, PAN Coordinator 120a has access to a lot of useful information, and options about what it can do to affect the performance of wireless network 100.
The problem that PAN Coordinator 120a has then is how to decide on what it should base its decision as to what to do with the information. In theory, PAN Coordinator 120a should decide what is “best” for wireless network 100. However, this problem is complicated by the nature of interferers to wireless network 100. Some interferers completely block out transmission on a channel, but many other interferers may just reduce the usable bandwidth of the channel. Also a given interferer affects messages between different pairs of networked nodes 120 differently, for instance a distant high duty cycle interferer might block reception of almost all messages from distant nodes 120 completely, but hardly affect nearby nodes 120 at all.
Given that in many cases it is not possible to have all nodes 120 running in an environment completely free of any interference, a problem arises as to what the “optimal” situation is that PAN Coordinator 120a should try to achieve, and on what criteria it should base its trade-off decisions.
Accordingly, it would be desirable to provide a method of employing channel condition estimates in order to make a decision as to whether or not to change one or more channels on which a wireless network communicates. It would further be desirable to provide a device for deciding whether or not to change one or more channels on which a wireless network communicates based on estimates of channel interference for one or more wireless devices in the wireless network.
In one aspect of the invention, in a communication network comprising a plurality of wireless devices, a method is provided for determining whether to change one or more communication channels over which the wireless devices communicate. The method comprises: receiving an indication of a selected operating mode for the communication network among a plurality of available operating modes, each operating mode having associated therewith a different communication channel change determination algorithm uniquely corresponding to that operating mode; receiving information related to one or more communication channel's availability for communications by one or more of the wireless devices; and determining whether to change one or more communication channels over which the wireless devices communicate by executing the communication channel change determination algorithm corresponding to the selected operating mode, using the received information related to one or more communication channel's availability for communications by one or more of the wireless devices.
In another aspect of the invention, in a communication network comprising a plurality of wireless devices, a method is provided for determining whether to change one or more communication channels over which the wireless devices communicate. The method comprises: receiving a plurality of configuration parameters for the communication network; receiving information related to one or more communication channel's availability for communications by one or more of the wireless devices; and determining whether to change one or more communication channels over which the wireless devices communicate by executing a communication channel change determination algorithm using the configuration parameters and the received information related to one or more communication channel's availability for communications by one or more of the wireless devices.
In a further aspect of the invention, in a communication network comprising a plurality of wireless devices, a device is provided for determining whether to change one or more communication channels over which the wireless devices communicate. The device comprises: means for receiving an indication of a selected operating mode for the communication network among a plurality of available operating modes, each operating mode having associated therewith a different communication channel change determination algorithm uniquely corresponding to that operating mode; means for receiving information related to one or more communication channel's availability for communications by one or more of the wireless devices; and means for determining whether to change one or more communication channels over which the wireless devices communicate by executing the communication channel change determination algorithm corresponding to the selected operating mode, using the received information related to one or more communication channel's availability for communications by one or more of the wireless devices.
In yet another aspect of the invention, in a communication network comprising a plurality of wireless devices, a device determines whether to change one or more communication channels over which the wireless devices communicate. The device comprises: means for receiving a plurality of configuration parameters for the communication network; means for receiving information related to one or more communication channel's availability for communications by one or more of the wireless devices; and means for determining whether to change one or more communication channels over which the wireless devices communicate by executing a communication channel change determination algorithm using the configuration parameters and the received information related to one or more communication channel's availability for communications by one or more of the wireless devices.